Oligomeriser with an improved feed system

ABSTRACT

In an embodiment, a reactor for carrying out a melt transesterification reaction at a reactor temperature of 160 to 300° C. and a reactor pressure of 5 to 200 mbar, comprises a cylindrical tank comprising a top, a side, and a bottom, wherein the bottom is convex, extending away from the top; a stirring shaft disposed within the cylindrical tank along an axis thereof so that it is rotatable from outside of the cylindrical tank; a stirring blade extending from the stirring shaft in the cylindrical tank; a reactant solution inlet located on the bottom; and a reaction solution outlet located on the bottom. The reactor can be used for the polymerization of a polycarbonate oligomer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of European Patent ApplicationSerial No. 17382424 filed Jun. 30, 2017. The related application isincorporated herein in its entirety by reference.

BACKGROUND

Polycarbonate is widely used in many engineering applications as it hasexcellent mechanical properties, such as impact resistance and heatresistance, and also has excellent transparency. In a typical methodthat is industrially used for producing polycarbonate, a bisphenol, suchas Bisphenol A (BPA), and a carbonate precursor, such as diphenylcarbonate (DPC), are reacted in an ester exchange method in a moltenstate. This melt polymerization is often referred to as a meltpolycondensation process or transesterification process. The resultingpolycarbonate can be extruded or otherwise processed, and can becombined with additives such as dyes and UV stabilizers.

The melt polymerization process though can result in polycarbonateshaving an increased yellowness index. Methods of preparing polycarbonatewith increased control of the polymerization are therefore desired.

BRIEF SUMMARY

Disclosed herein is a bottom feed reactor and uses thereof.

In an embodiment, a reactor for carrying out a melt transesterificationreaction at a reactor temperature of 160 to 300° C. and a reactorpressure of 5 to 200 mbar, comprises a cylindrical tank comprising atop, a side, and a bottom, wherein the bottom is convex, extending awayfrom the top; a stirring shaft disposed within the cylindrical tankalong an axis thereof so that it is rotatable from outside of thecylindrical tank; a stirring blade extending from the stirring shaft inthe cylindrical tank; a reactant solution inlet located on the bottom;and a reaction solution outlet located on the bottom.

In another embodiment, a method of melt polymerizing a polycarbonate,comprises adding a precursor solution comprising a polycarbonateprecursor to the reactor of any one or more of the preceding embodimentsthrough the reactant solution inlet; reacting the polycarbonateprecursor at the reactor temperature of 160 to 300° C., preferably, 160to 240° C. and the reactor pressure of 5 to 200 mbar to form a mixedsolution comprising a polycarbonate oligomer having a weight averagemolecular weight that is greater than that of the polycarbonateprecursor; withdrawing the mixed solution from the reaction solutionoutlet; and polymerizing the polycarbonate oligomer to form thepolycarbonate.

The above described and other features are exemplified by the followingfigures, detailed description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures are exemplary, non-limiting embodiments, wherein the likeelements are numbered alike. Several of the figures are illustrative ofthe examples, which are not intended to limit the disclosure to thematerials, conditions, or process parameters set forth herein.

FIG. 1 is an illustration of an embodiment of a bottom feed reactor;

FIG. 2 is an illustration of an embodiment of a bottom feed reactor;

FIG. 3 is an illustration of the computational fluid dynamics evaluationof the side feed reactor of Example 1;

FIG. 4 is a blown up illustration of a portion of FIG. 3 ;

FIG. 5 is an illustration of the computational fluid dynamics evaluationof the side feed reactor Example 1 showing a quick path to exit for thesolution;

FIG. 6 is an illustration of the computational fluid dynamics evaluationof the bottom feed reactor Example 2 showing an increased path to exitfor the solution; and

FIG. 7 is a graphical illustration of the residence time profile ofExamples 3-5.

DETAILED DESCRIPTION

Melt polymerization is an industrially used process to makepolycarbonate by reacting a bisphenol and a carbonate compound in themolten form. The bisphenol and the carbonate compound are added to amonomer mixing tank along with a quaternary catalyst, where someoligomerization starts, as is evidenced by production of a phenolbyproduct. From the monomer mixing tank, the melt is added to a seriesof oligomerization units. When the mixing behavior in these reactors wasstudied, multiple flow paths were identified in the reactor as shown inFIG. 3 and FIG. 4 . In reviewing the flow paths, it was found that theexisting location of the inlet, on the side of the cylindrical tank, wasnot well positioned. Though the inlet and the outlet are located farfrom each other physically, due to the circulating flow pattern in thereactor, a significant amount of material that enters through the inletcan quickly reach the outlet as shown in FIG. 3 . This early exiting ofmaterial ultimately resulted in a broad residence time distribution inthe reactor.

It was surprisingly discovered that early access of the feed material tothe reaction solution outlet could be reduced by positioning thereactant solution inlet on the bottom of the tank. In this manner, eventhough the reactant solution inlet is physically closer to the reactionsolution outlet, it is further upstream in the flow pattern, resultingin an increased path length of the feed material to reach the reactionsolution outlet (as is illustrated in FIG. 6 ) ultimately resulting inan improvement (characterized by a reduction in the spread of thedistribution) in the residence time distribution in the reactor. It wasfurther surprisingly discovered that by relocating the reactant solutioninlet to the bottom of the tank, the channeling of fluid through lowerresistant paths that otherwise occurs when the solution viscosity ishigh, for example, greater than 3 Pascal seconds (Pa·s), could besignificantly reduced, ultimately resulting in a further improvement inthe residence time distribution. As used herein, the viscosity isdetermined using a parallel plate rheometer, AR-G2 from TA Instruments,using 25 millimeters (mm) diameter plates having a 0.5 mm gap betweenthe plates. The measurements were made at a temperature of 250 to 300degrees Celsius (° C.) and varying frequency from 100 and 1,000 inverseseconds (s⁻¹). The improved residence time distribution in the reactormay result in a reduction of degradation and discoloration of theresultant polycarbonate.

FIG. 1 and FIG. 2 are illustrations of embodiments of the improved,bottom feed reactor 10. FIG. 1 illustrates that reactor 10 can comprisecylindrical tank 12 comprising a top, a side, and a bottom, wherein thebottom is convex, extending away from the top. Stirring shaft 14 isdisposed within cylindrical tank 12 along axis 100 thereof so that it isrotatable from outside of cylindrical tank 12. Stirring blade 16 extendsfrom stirring shaft 14 in cylindrical tank 12. Both reactant solutioninlet 40 and reaction solution outlet 20 are located on the bottom ofcylindrical tank 12. The reactor is a vertical reactor such that axis100 is perpendicular (within 10°, or 0 to 5°, or 0 to 1°) to at leastone of a plane tangent to the bottom of the cylindrical tank or a topfluid plane as defined by a top surface (110) of a resting liquidpresent in the cylindrical tank.

The shape of the stirring blade is not particularly limited. Thestirring blade can comprise a flat plate impeller. The flat plateimpeller can be rectangular, square, triangular, trapezoidal, irregular,or the like. The flat plate impeller can have a plurality of openings,for example, openings 18 illustrated in FIG. 2 .

The stirring blade can comprise, at least one impeller (for example, ahydrofoil impeller), for example, 1 to 5, or 2 to 4, or 1 to 2 impellerscan extend from the stirring shaft. The impeller can comprise 2 to 5blades, or 2 to 4 blades, or 3 blades. For example, each impeller can bea three-blade impeller.

A total volume of the cylindrical tank can be greater than or equal to10 meters cubed (m³), or 20 to 100 m³, or 20 to 50 m³. The cylindricaltank can hold greater than or equal to 5,000 liters (L), or 5,000 to50,000 L, or 5,000 to 15,000 L of liquid. The cylindrical tank can havean inner reactor diameter, D_(T), of 1 to 10 meters (m), or 2 to 5 m.

A reactant solution inlet is located on the bottom of the cylindricaltank, for example, as illustrated reactant solution inlet 40 in FIG. 1and FIG. 2 . The reactant solution inlet can allow for a polycarbonateprecursor solution to be added to the reactor. One or both of additionalcatalyst and additional monomer can be added to the reactor through thesame or through a different inlet that may or may not be located on thebottom of the cylindrical tank. In order to achieve optimum mixing, allof the inlets can be located on the bottom of the cylindrical tank.

The reactant solution inlet can be located outside of a rotation columnof the stirring blade. For example, FIG. 2 illustrates that the distancem of inner edge 6 from axis 100 can be greater than or equal to one halfof the outer diameter D of lower edge 8 of stirring blade 16 (m≥D/2).

A reaction solution outlet can be located on the side of the cylindricaltank. A reaction solution outlet can be located on the bottom of thecylindrical tank. If located on the bottom of the cylindrical tank, thereaction solution outlet can be concentrically located on a central axisof the cylindrical tank. For example, FIG. 1 and FIG. 2 illustratereaction solution outlet 20 concentrically located on axis 100 ofcylindrical tank 12.

The reactor can comprise a heat exchanger. The heat exchanger can be aninternally located heat exchanger that is located inside the cylindricaltank. The heat exchanger can comprise a heating jacket in physicalcontact with at least a portion of the outside wall of the cylindricaltank. The heat exchanger can comprise an externally located heatexchanger.

If the reactor comprises the internally located heat exchanger, theinternally located heat exchanger can comprise one or more internalheating coils located in the cylindrical tank. The internally locatedheat exchanger can be located in the cylindrical tank at a distance fromthe axis of greater than half of the outer diameter of the stirringblade at the same height in the cylindrical tank. FIG. 3 is anillustration of a cylindrical reactor that comprises 19 heat exchangercoils 64 on four sets of four supports 66. An inner diameter of each ofthe circular coils independently can be greater than an outermostdiameter of the stirring blade. In other words, a rotation columndefined by the rotation of the stirring blade, as illustrated in FIG. 2as rotation column 60, can be free of heat exchanger coils 64.

If the reactor comprises the externally located heat exchanger, thereactant solution inlet can be in fluid communication with theexternally located heat exchanger. For example, a heated stream leavingthe externally located heat exchanger can be combined with a solutionstream upstream of the reactant solution inlet and added as a combinedstream. Conversely, the heated stream can be added to the cylindricaltank through a recirculation inlet that is different from the reactantsolution inlet. The recirculation inlet can be located on the top of thecylindrical tank. The recirculation inlet can be located on the side ofthe cylindrical tank. The recirculation inlet can be located on thebottom of the cylindrical tank.

The reaction solution outlet can be in fluid communication with theexternally located heat exchanger. For example, a mixed solution streamexiting the reaction solution outlet can be split (for example, using aY-junction or a T-junction) into at least two streams, where one of thestreams is a recirculation stream that connects to the externallylocated heat exchanger. Conversely, the recirculation stream can exitthe cylindrical tank via a recirculation outlet that is separate fromthe reaction solution outlet. The recirculation outlet can be located onthe side of the cylindrical tank. The recirculation outlet can belocated on the bottom of the cylindrical tank.

The cylindrical tank can comprise a reactant solution inlet, a reactionsolution outlet, a recirculation inlet, and a recirculation outlet. Boththe recirculation inlet and the recirculation outlet can be located onthe bottom of the cylindrical tank. The recirculation outlet can belocated on the bottom of the cylindrical tank and the recirculationinlet can be located on the side of the cylindrical tank. Thecylindrical tank can comprise a reactant solution inlet, a reactionsolution outlet, and a recirculation inlet, where the reaction solutionoutlet is in fluid communication with both a second reactor via a mixedsolution stream and the externally located heat exchanger viarecirculation stream.

The externally located heat exchanger can comprise 1 or more externallylocated heat exchangers. When two or more externally located heatexchangers are present, the externally located heat exchangers can beconfigured in series and/or in parallel with each other. The cylindricaltank can be free of an internally located heat exchanger.

The reactor can be used to prepare a polycarbonate oligomer from aprecursor solution. The precursor solution comprising the polycarbonateprecursor can be formed in a monomer mixing unit. The monomer mixingunit can be maintained at atmospheric pressure and at a temperature of100 to 250° C., or 150 to 200° C., or 165 to 185° C. The polycarbonateprecursor can comprise a carbonate precursor, a bisphenol, a catalyst,and optionally a low molecular weight oligomer. The bisphenol and thecarbonate precursor in the precursor solution can be present in a molarratio of 0.5:1 to 1.5:1, or 0.9:1 to 1.1:1, or 0.99:1 to 1.01:1.

The method of mixing a precursor solution in the reactor, can compriseadding the precursor solution comprising a polycarbonate precursor tothe reactor through a reactant solution inlet located on a bottom sideof the cylindrical tank; mixing and polymerizing the polycarbonateprecursor at a reactor temperature and a reactor pressure to form apolycarbonate oligomer; and withdrawing a mixed solution comprising thepolycarbonate oligomer having a weight average molecular weight that isgreater than that of the polycarbonate precursor from a reactionsolution outlet. The method can comprise removing a recirculation streamfrom the cylindrical reactor, flowing the recirculation stream throughan externally located heat exchanger to form a heated stream, andreintroducing the heated stream to the cylindrical reactor. The reactortemperature can be 160 to 300° C. or 160 to 280° C., or 160 to 240° C.,or 200 to 270° C., or 275 to 300° C. The reactor pressure can be 5 to200 millibar absolute (mbar), or 30 to 200 mbar, or 2 to 25 mbar. Theaverage residence time of the precursor solution in the reactor can begreater than or equal to a comparison average residence time of theprecursor solution added to the same reactor but through a side feeder.The average residence time of the precursor solution in the reactor canbe 0.1 to 15 hours.

The mixing can result in the formation of an axial flow pattern, forexample, as illustrated in FIG. 6 . As used herein, the axial flowpattern refers to the fluid flow flowing in the direction of thestirring shaft towards the bottom of the tank, flowing from the bottomof the tank towards the side of the tank, and flowing upwards along theside of the tank to form a complete circulation loop. A good axial flowpattern can ensure that there are no dead pockets or poorly mixed zonesin the reactor and can provide a good volumetric renewal rate to ensurethe produced phenol leaves the reactor.

The mixing can occur at a rotation speed of the stirring shaft of 40 to100 revolutions per minute (rpm). The mixing can achieve a normalizedsurface refresh rate of greater than or equal to 0.03 inverse seconds(s⁻¹), or 0.04 to 0.4 s⁻¹, or 0.06 to 0.1 s⁻¹. As used herein, thenormalized surface refresh rate is the volume of solution that passesacross a plane located 200 mm below the liquid surface level per secondper total volume of solution in the reactor (m³/s·m³ or s⁻¹). The mixingtime can be less than or equal to 60 seconds (s), or 20 to 50 s.

The mixed solution can have a mixed solution viscosity that is greaterthan a precursor solution viscosity of the precursor solution. Forexample, the precursor solution can have a precursor solution viscositythat is less than or equal to 0.05 Pa·s and the mixed solution can havea mixed solution viscosity of greater than or equal to 0.05 Pa s, orgreater than or equal to 0.5 Pa·s, or 0.05 to 0.5 Pa·s, or greater thanor equal to 2.5 Pa·s, or 0.15 to 10 Pas, or 0.5 to 10 Pa·s.

When the bottom feed reactor is used in a melt polycarbonatepolymerization plant, it can be used as an oligomerization reactor (alsoreferred to as an oligomeriser). The oligomerization reactor can be inseries with two or more oligomerizers. One or more of the oligomeriserscan be bottom feed reactors. For example, in a melt polymerization (alsoreferred to herein as a melt transesterification reaction), a reactantsolution inlet of a first oligomeriser can be in fluid communicationwith a monomer mixing tank, the reaction solution outlet of the firstoligomeriser can be in fluid communication with a second reactor inletof a second oligomeriser, and a second reactor outlet of the secondoligomeriser can be in fluid communication with a polymerizationreactor. At least one of the first oligomeriser or the secondoligomeriser can be a bottom feed reactor. For example, the firstoligomeriser can be a side feed reactor having two three-blade impellersextending from the stirring shaft and the second oligomeriser can be abottom feed reactor having a flat plate impeller extending from thestirring shaft. Conversely, both the first oligomeriser and the secondoligomeriser can be bottom feed reactors.

The mixed solution can be added to a second reactor and the method cancomprise adding the mixed solution to the second reactor via an inletthat can be located on the bottom of the second reactor, mixing andfurther polymerizing the mixed solution at a second temperature greaterthan the reactor temperature and a second pressure less than the reactorpressure, and withdrawing an oligomer solution comprising a highmolecular weight polycarbonate oligomer having a weight averagemolecular weight that is greater than that of the polycarbonateoligomer. For example, the high molecular weight polycarbonate oligomercan have a weight average molecular weight of 1.5 to 15 kilodaltons, or8 to 12 kilodaltons, or 8 to 20 kilodaltons based on polycarbonatestandards. The high molecular weight polycarbonate oligomer can have aviscosity of 1 to 10 Pa·s. The high molecular weight polycarbonateoligomer can then be polymerized in one or more polymerization vessels,for example, one or more wire wetting fall polymerization units,horizontal polymerizers, vertical polymerizers, reactive extruders, or acontinuously stirred tank.

The second reactor can comprise a second cylindrical tank comprising asecond top, a second side, and a second bottom, wherein the secondbottom is convex. extending away from the second top; a second stirringshaft disposed within the second cylindrical tank along a second axisthereof so that it is rotatable from outside of the second cylindricaltank; a second stirring blade extending from the second stirring shaftin the second cylindrical tank; a second reactant solution inlet locatedon the second bottom; and a second reaction solution outlet located onthe second bottom. It is noted that the term “second” is used forclarity to distinguish from the “first” reactor and that the term“downstream” could likewise be used.

The first reactor temperature can be 160 to 300° C., or 160 to 275° C.,or 160 to 250° C., or 200 to 270° C. or 230 to 270° C. The first reactorpressure can be 50 to 200 mbar, or 75 to 200 mbar. The mixed solutionviscosity can be 0.05 to 1 Pa·s, or 0.05 to 0.5 Pa·s. The second reactortemperature can be 250 to 300° C. or 270 to 300° C. The second reactorpressure can be 5 to 50 mbar, or 10 to 40 mbar. The oligomer solutionviscosity can be 0.5 to 10 Pa·s, or 1 to 5 Pa·s, or greater than orequal to 1 Pa·s.

The polycarbonate can then be extruded in an extruder where an optionalquencher and an additive can be added to the molten polycarbonate. Theextruder can be a twin-screw extruder and at least one of the componentscan be incorporated into the composition by feeding directly into theextruder at the throat and/or downstream of the throat through, forexample, a side stuffer.

The carbonate precursor can comprise a diaryl carbonate ester, forexample, diphenyl carbonate or an activated diphenyl carbonate havingelectron-withdrawing substituents on each aryl, for example, at leastone of bis(4-nitrophenyl)carbonate, bis(2-chlorophenyl)carbonate,bis(4-chlorophenyl)carbonate, bis(methyl salicyl)carbonate,bis(4-methylcarboxylphenyl) carbonate, bis(2-acetylphenyl) carboxylate,or bis(4-acetylphenyl) carboxylate. The diaryl carbonate ester can befree of an activated diphenyl carbonate having electron-withdrawingsubstituents on each aryl. For example, the diaryl carbonate ester canbe free of bis(4-nitrophenyl)carbonate, bis(2-chlorophenyl)carbonate,bis(4-chlorophenyl)carbonate, bis(methyl salicyl)carbonate,bis(4-methylcarboxylphenyl) carbonate, bis(2-acetylphenyl) carboxylate,and bis(4-acetylphenyl) carboxylate. The diaryl carbonate ester can befree of bis(methyl salicyl)carbonate. As used herein, “can be free of”refers to none of the compounds being added in the melt polymerization,for example, less than or equal to 10 ppm, for example, 0 ppm of thecompound being present. The carbonate precursor can comprise diphenylcarbonate.

The bisphenol can comprise a dihydroxy compound of the formula HO—R¹—OH,wherein the R¹ group can contain an aliphatic, an alicyclic, or anaromatic moiety. For example, the bisphenol can have the formula (2)

HO-A¹-Y¹-A²-OH  (2)

wherein each of A¹ and A² is a monocyclic divalent aromatic group and Y¹is a single bond or a bridging group having one or more atoms thatseparate A¹ from A². One atom can separate A¹ from A².

The bisphenol can have the formula (3)

wherein R^(a) and R^(b) are each independently a halogen, C₁₋₁₂ alkoxy,or C₁₋₁₂ alkyl; and p and q are each independently integers of 0 to 4.It will be understood that R^(a) is hydrogen when p is 0, and likewiseR^(b) is hydrogen when q is 0. Also in formula (3), X^(a) is a bridginggroup connecting the two hydroxy-substituted aromatic groups, where thebridging group and the hydroxy substituent of each C₆ arylene group aredisposed ortho, meta, or para (specifically, para) to each other on theC₆ arylene group. The bridging group X^(a) can be single bond, —O—, —S—,—S(O)—, —S(O)₂—, —C(O)—, or a C₁₋₁₈ organic bridging group. The C₁₋₁₈organic bridging group can be cyclic or acyclic, aromatic ornon-aromatic, and can further comprise heteroatoms, for example,halogens, oxygen, nitrogen, sulfur, silicon, or phosphorous. The C₁₋₁₈organic bridging group can be disposed such that the C₆ arylene groupsconnected thereto are each connected to a common alkylidene carbon or todifferent carbons of the C₁₋₁₈ organic bridging group. p and q can eachbe 1, and R^(a) and R^(b) are each a C₁₋₃ alkyl group, specifically,methyl, disposed meta to the hydroxy group on each arylene group.

X^(a) can be a substituted or unsubstituted C₃₋₁₈ cycloalkylidene, aC₁₋₂₅ alkylidene of formula —C(R^(c))(R^(d))— wherein R^(c) and R^(d)are each independently hydrogen, C₁₋₁₂ alkyl, C₁₋₁₂ cycloalkyl, C₇₋₁₂arylalkyl, C₁₋₁₂ heteroalkyl, or cyclic C₇₋₁₂ heteroarylalkyl, or agroup of the formula —C(═R^(e))— wherein R^(e) is a divalent C₁₋₁₂hydrocarbon group. Groups of this type include methylene,cyclohexylmethylene, ethylidene, neopentylidene, and isopropylidene, aswell as 2-[2.2.1]-bicycloheptylidene, cyclohexylidene, cyclopentylidene,cyclododecylidene, and adamantylidene.

X^(a) can be a C₁₋₁₈ alkylene group, a C₃₋₁₈ cycloalkylene group, afused C₆₋₁₈ cycloalkylene group, or a group of the formula —B¹-G-B²—wherein B¹ and B² are the same or different C₁₋₆ alkylene group and G isa C₃₋₁₂ cycloalkylidene group or a C₆₋₁₆ arylene group. For example,X^(a) can be a substituted C₃₋₁₈ cycloalkylidene of formula (4)

wherein R^(r), R^(p), R^(t), and R are each independently hydrogen,halogen, oxygen, or C₁₋₁₂ hydrocarbon groups; Q is a direct bond, acarbon, or a divalent oxygen, sulfur, or —N(Z)— where Z is hydrogen,halogen, hydroxy, C₁₋₁₂ alkyl, C₁₋₁₂ alkoxy, or C₁₋₁₂ acyl; r is 0 to 2,t is 1 or 2, q is 0 or 1, and k is 0 to 3, with the proviso that atleast two of R^(r), R^(p), R^(q), and R^(t) taken together are a fusedcycloaliphatic, aromatic, or heteroaromatic ring. It will be understoodthat where the fused ring is aromatic, the ring as shown in formula (4)will have an unsaturated carbon-carbon linkage where the ring is fused.When k is one and q is 0, the ring as shown in formula (4) contains 4carbon atoms, when k is 2, the ring as shown in formula (4) contains 5carbon atoms, and when k is 3, the ring contains 6 carbon atoms. Twoadjacent groups (e.g., R^(q) and R^(t) taken together) can form anaromatic group or R^(q) and R^(t) taken together can form one aromaticgroup and R^(r) and R^(p) taken together form a second aromatic group.When R^(q) and R^(t) taken together form an aromatic group, R^(p) can bea double-bonded oxygen atom. i.e., a ketone.

Specific examples of bisphenol compounds of formula (3) include1,1-bis(4-hydroxyphenyl) methane, 1,1-bis(4-hydroxyphenyl) ethane,2,2-bis(4-hydroxyphenyl) propane (hereinafter “bisphenol A” or “BPA”),2,2-bis(4-hydroxyphenyl) butane, 2,2-bis(4-hydroxyphenyl) octane,1,1-bis(4-hydroxyphenyl) propane, 1-bis(4-hydroxyphenyl) n-butane,2,2-bis(4-hydroxy-2-methylphenyl) propane,1,1-bis(4-hydroxy-t-butylphenyl) propane, 3,3-bis(4-hydroxyphenyl)phthalimidine, 2-phenyl-3,3-bis(4-hydroxyphenyl) phthalimidine (PPPBP),and 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (DMBPC). Combinationscomprising at least one of the foregoing bisphenols can also be used.The bisphenol can comprise bisphenol A, in which each of A¹ and A² canbe p-phenylene, and Y¹ can be isopropylidene in formula (3).

The resultant “polycarbonate” as used herein is derived from thecarbonate compound and the bisphenol and can have repeating structuralcarbonate units of formula (1)

in which the R¹ groups contain aliphatic, alicyclic, and/or aromaticmoieties (e.g., greater than or equal to 30 percent, specifically,greater than or equal to 60 percent, of the total number of R¹ groupscan contain aromatic moieties and the balance thereof are aliphatic,alicyclic, or aromatic). Optionally, each R¹ can be a C₆₋₃₀ aromaticgroup that can contain at least one aromatic moiety. R¹ can be derivedfrom the bisphenol.

The precursor solution can comprise at least one of a quaternarycompound or an alkali catalyst. The precursor solution can comprise aquaternary compound and an alkali catalyst can be added to the reactoras a separate catalyst stream.

The quaternary catalyst comprises at least one of a quaternary ammoniumcompound or a quaternary phosphonium compound. The quaternary ammoniumcompound can be a compound of the structure (R⁴)₄N⁺X⁻, wherein each R⁴is the same or different, and is a C₁₋₂₀ alkyl, a C₄₋₂₀ cycloalkyl, or aC₄₋₂₀ aryl; and X⁻ is an organic or inorganic anion, for example, ahydroxide, halide, carboxylate, sulfonate, sulfate, formate, carbonate,or bicarbonate. Examples of organic quaternary ammonium compoundsinclude tetramethyl ammonium hydroxide, tetrabutyl ammonium hydroxide,tetramethyl ammonium acetate, tetramethyl ammonium formate, andtetrabutyl ammonium acetate.

The quaternary phosphonium compound can be a compound of the structure(R⁵)₄P⁺X⁻, wherein each R⁵ is the same or different, and is a C₁₋₂₀alkyl, a C₄₋₂₀ cycloalkyl, or a C₄₋₂₀ aryl; and X⁻ is an organic orinorganic anion, for example, a hydroxide, phenoxide, halide,carboxylate, for example, acetate or formate, sulfonate, sulfate,formate, carbonate, or bicarbonate. Where X⁻ is a polyvalent anion, forexample, carbonate or sulfate, it is understood that the positive andnegative charges in the quaternary ammonium and phosphonium structuresare properly balanced. For example, where R²⁰ to R²³ are each methylsand X⁻ is carbonate, it is understood that X⁻ represents 2(CO₃ ⁻²).

Examples of organic quaternary phosphonium compounds include tetramethylphosphonium hydroxide, tetramethyl phosphonium acetate, tetramethylphosphonium formate, tetrabutyl phosphonium hydroxide, tetraethylphosphonium acetate, tetrapropyl phosphonium acetate, tetrabutylphosphonium acetate (TBPA), tetrapentyl phosphonium acetate, tetrahexylphosphonium acetate, tetraheptyl phosphonium acetate, tetraoctylphosphonium acetate, tetradecyl phosphonium acetate, tetradodecylphosphonium acetate, tetratolyl phosphonium acetate, tetramethylphosphonium benzoate, tetraethyl phosphonium benzoate, tetrapropylphosphonium benzoate, tetraphenyl phosphonium benzoate, tetraethylphosphonium formate, tetrapropyl phosphonium formate, tetraphenylphosphonium formate, tetramethyl phosphonium propionate, tetraethylphosphonium propionate, tetrapropyl phosphonium propionate, tetramethylphosphonium butyrate, tetraethyl phosphonium butyrate, tetrapropylphosphonium butyrate, tetraphenyl phosphonium acetate (TPPA), andtetraphenyl phosphonium phenoxide (TPPP). The quaternary catalyst cancomprise at least one of tetrabutyl phosphonium acetate, TPPP, or TPPA.

The amount of the quaternary catalyst can be added based upon the totalnumber of moles of bisphenol employed in the polymerization reaction.When referring to the ratio of catalyst, for example, phosphonium salt,to all bisphenols employed in the polymerization reaction, it isconvenient to refer to moles of phosphonium salt per mole of thebisphenol(s), meaning the number of moles of phosphonium salt divided bythe sum of the moles of each individual bisphenol present in thereaction mixture. The amount of the optional quaternary catalyst (e.g.,organic ammonium or phosphonium salts) can each independently beemployed in an amount of 1×10⁻² to 1×10⁻⁵, or 1×10⁻³ to 1×10⁻⁴ moles pertotal mole of the bisphenol(s) in the monomer mixture.

The alkali catalyst comprises a source of one or both of alkali ions andalkaline earth ions. The sources of these ions can include alkalineearth hydroxides, for example, magnesium hydroxide and calciumhydroxide. Sources of alkali metal ions can include the alkali metalhydroxides, for example, at least one of lithium hydroxide, sodiumhydroxide, or potassium hydroxide. Examples of alkaline earth metalhydroxides are calcium hydroxide and magnesium hydroxide. The alkalicatalyst can comprise sodium hydroxide. Other possible sources ofalkaline earth and alkali metal ions include at least one of salts ofcarboxylic acids (for example, sodium acetate) or derivatives ofethylene diamine tetraacetic acid (EDTA) (for example, EDTA tetrasodiumsalt and EDTA magnesium disodium salt). For example, the alkali catalystcan comprise at least one of alkali metal salt(s) of a carboxylic acidor alkaline earth metal salt(s) of a carboxylic acid. In anotherexample, the alkali catalyst comprises Na₂Mg EDTA or a salt thereof.

The alkali catalyst can also, or alternatively, comprise salt(s) of anon-volatile inorganic acid. For example, the alkali catalyst cancomprise salt(s) of a non-volatile inorganic acid, for example, at leastone of NaH₂PO₃, NaH₂PO₄, Na₂HPO₃, KH₂PO₄, CsH₂PO₄, or Cs₂HPO₄.Alternatively, or in addition, the alkali catalyst can comprise mixedalkali metal salt(s) of phosphoric acid, for example, at least one ofNaKHPO₄, CsNaHPO₄, or CsH₂PO₄. The alkali catalyst can comprise KNaHPO₄,wherein a molar ratio of Na to K is 0.5 to 2.

The alkali catalyst typically can be used in an amount sufficient toprovide 1×10⁻² to 1×10⁻⁸ moles, or 1×10⁻⁴ to 1×10⁻⁷ moles of metalhydroxide per mole of the bisphenol(s).

Quenching of the transesterification catalysts and any reactivecatalysts residues with an acidic compound after polymerization can becompleted can also be useful in some melt polymerization processes.Among the many quenchers that can be used are alkyl sulfonic esters ofthe formula R⁸SO₃R⁹ wherein R⁸ is hydrogen. C₁₋₁₂ alkyl, C₆₋₁₈ aryl, orC₇₋₁₉ alkylaryl, and R⁹ is C₁₋₁₂ alkyl, C₆₋₁₈ aryl, or C₇₋₁₉ alkylaryl.Examples of quenchers include benzenesulfonate, p-toluenesulfonate,methylbenzene sulfonate, ethylbenzene sulfonate, n-butylbenzenesulfonate, octyl benzenesulfonate and phenyl benzenesulfonate,methyl p-toluenesulfonate, ethyl p-toluenesulfonate, n-butyl p-toluenesulfonate, octyl p-toluenesulfonate, and phenyl p-toluenesulfonate. Inparticular, the quencher can comprise an alkyl tosylate, for example,n-butyl tosylate.

The following examples are provided to illustrate the bottom feedreactor. The examples are merely illustrative and are not intended tolimit devices made in accordance with the disclosure to the materials,conditions, or process parameters set forth therein.

EXAMPLES Example 1: Flow Evaluation of a Side Feed Reactor

A computational fluid dynamics evaluation of fluid flow in a side feedreactor was performed using ANSYS CFD software. In the evaluation, areactor as illustrated in FIG. 3 was modelled, where the stirringapparatus was rotated at a rate of 66 revolutions per minute (rpm), thereactor had a volume of 6.88 m³, the solution density was 1,020kilograms per meter cubed (kg/m), the temperature was 280° C., the massflow rate was 9,500 kilograms per hour (kg/hr), and the solutionviscosity was 2 Pa·s.

The resulting flow pattern is shown in FIG. 3 , FIG. 4 , and FIG. 5 ,where FIG. 4 is a blown up illustration of the box outlined in FIG. 3 .The figures illustrate that the channeling of fluid through lowerresistant paths was significant when the solution viscosity was high.FIG. 5 further illustrates that, although the reactant solution inlet 40and the reaction solution outlet 20 of the tank are located at anincreased distance from one another, being across the tank, the viscoussolution that enters through the inlet can quickly reach the reactionsolution outlet 20 along the path of the dotted line, S, which canultimately result in a broad residence time distribution of the solutionin the reactor.

Example 2: Flow Evaluation of a Bottom Feed Reactor

A computational flow dynamics evaluation was performed in accordancewith Example 1, except that the reactant solution inlet was located atthe bottom of the reactor.

The resulting flow pattern is shown in FIG. 6 . FIG. 6 illustrates thatthe overall flow path of the solution entering from a bottom feed isincreased, for example, along dotted line, B, as compared to dotted lineS, which is merely illustrated in FIG. 6 for comparative purposes. Thisincreased flow path results in an increased residence time in thereactor for some early leaving fluid elements.

Example 3-5: Residence Time Evaluation

Residence time evaluations were performed, where, after steady state wasachieved, a tracer was injected upstream of the reactor and theconcentration of the tracer in a line downstream of the reactor wasdetermined with time. In Example 3, the simulation was performed inaccordance with the side feed reactor of Example 1. In Example 4, thesimulation was performed in accordance with the side feed reactor ofExample 3 except the viscosity of the solution was increased to 3.2Pa·s. In Example 5, the simulation was performed in accordance with thebottom feed reactor of Example 2, except the viscosity of the solutionwas increased to 3.2 Pa·s. The concentration profiles were then comparedto that of an ideal continuously stirred tank (CSTR). The results areillustrated in FIG. 7 .

FIG. 7 shows that the side feed reactor of Example 3 at a viscosity of 2Pa·s, achieves almost ideal mixing. When the viscosity is increased to3.2 Pa·s, as in Example 4, two peaks in the residence time evaluation atearly times are observed, indicating the formation of shorter flow pathsin the reactor. Surprisingly, merely by utilizing a bottom feed reactor,the residence time in the reactor of the more viscous solution wasincreased, where FIG. 7 clearly shows the delayed peak formation as ofExample 5 as compared to Example 4. FIG. 7 further shows that Example 5displayed a single peak as compared to the double peak of Example 4. Thepresence of only a single peak in Example 5 indicates that the formationof a shorter flow path to exit was beneficially avoided. These resultsclearly indicate that using the bottom feed reactor, a longer residencetime in the reactor is achieved for some early leaving fluid elements.When used therefore in an oligomerization reaction, the longer residencetime can ultimately result in an increased reaction time for thereactants in the reactor, potentially allowing for the increased highermolecular weight with a reduced polydispersity.

Set forth below are non-limiting embodiments of the present disclosure.

Embodiment 1: A reactor for carrying out a melt transesterificationreaction at a reactor temperature of 160 to 300° C. and a reactorpressure of 5 to 200 mbar, comprising: a cylindrical tank comprising atop, a side, and a bottom, wherein the bottom is convex, extending awayfrom the top; a stirring shaft disposed within the cylindrical tankalong an axis thereof so that it is rotatable from outside of thecylindrical tank; a stirring blade extending from the stirring shaft inthe cylindrical tank; a reactant solution inlet located on the bottom;and a reaction solution outlet located on the bottom. The reactor is avertical reactor where the axis of the stirring shaft is perpendicular(i.e. within 10°, or 0 to 50, or 0 to 1°) to at least one of a planetangent to the bottom of the cylindrical tank or a top fluid plane asdefined by a top surface of a resting liquid present in the cylindricaltank.

Embodiment 2: The reactor of Embodiment 1, wherein the reaction solutionoutlet is concentrically located on the axis of the cylindrical tank.

Embodiment 3: The reactor of any one or more of the precedingembodiments, wherein the stirring blade comprises a flat plate impelleroptionally having a plurality of openings.

Embodiment 4: The reactor of any one or more of the precedingembodiments, wherein the stirring blade comprises a three-bladeimpeller.

Embodiment 5: A method of melt polymerizing a polycarbonate, comprising:adding a precursor solution comprising a polycarbonate precursor to thereactor of any one or more of the preceding embodiments through thereactant solution inlet; reacting the polycarbonate precursor at thereactor temperature of 160 to 300° C., preferably, 160 to 240° C. andthe reactor pressure of 5 to 200 mbar to form a mixed solutioncomprising a polycarbonate oligomer having a weight average molecularweight that is greater than that of the polycarbonate precursor;withdrawing the mixed solution from the reaction solution outlet; andpolymerizing the polycarbonate oligomer to form the polycarbonate.

Embodiment 6: The method of Embodiment 5, wherein the mixed solution hasa mixed solution viscosity of 0.15 to 10 Pa s.

Embodiment 7: The method of any one or more of Embodiments 5 to 6,wherein the mixed solution has a mixed solution viscosity that isgreater than a precursor solution viscosity of the precursor solution.

Embodiment 8: The method of any one or more of Embodiments 5 to 7,wherein an average residence time of the precursor solution in thereactor is greater than a comparison average residence time of theprecursor solution added to a corresponding reactor that is the same asthe reactor but that adds the precursor solution through a side feeder,preferably, the residence time is 0.1 to 15 hours.

Embodiment 9: The method of any one or more of Embodiments 5 to 8,further comprising adding a catalyst to the reactor.

Embodiment 10: The method of any one or more of Embodiments 5 to 9,further comprising, prior to the polymerizing, directing the mixedsolution into a second reactor of any one or more of Embodiments 1 to 4;mixing the mixed solution at a second temperature greater than thereactor temperature and a second pressure less than the reactorpressure; and withdrawing an oligomer solution comprising a highmolecular weight polycarbonate oligomer having a weight averagemolecular weight that is greater than that of the polycarbonate oligomerfrom the reaction solution outlet.

Embodiment 11: The method of Embodiment 10, wherein the high molecularweight polycarbonate oligomer has a weight average molecular weight of1.5 to 15 kilodaltons based on polycarbonate standards.

Embodiment 12: The method of any one or more of Embodiments 5 to 11,wherein the precursor solution comprises bisphenol A and diphenylcarbonate.

Embodiment 13: A method of melt polymerizing a polycarbonate,comprising: adding a carbonate precursor, a bisphenol, and a quaternarycatalyst to a monomer mixing tank to form a precursor solution; addingthe precursor solution to a first oligomeriser and mixing andpolymerizing the polycarbonate precursor in the rust oligomeriser at afirst reactor temperature of 200 to 270° C., preferably, 245 to 265° C.,and a first reactor pressure of 50 to 200 mbar to form a polycarbonateoligomer having a first viscosity of 0.05 to 0.5 Pa·s; withdrawing amixed solution from the first oligomeriser comprising the polycarbonateoligomer having a weight average molecular weight that is greater thanthat of the polycarbonate precursor from the reaction solution outlet;directing the mixed solution into a second oligomeriser and mixing themixed solution at a second temperature of 275 to 300° C. and a secondpressure of 2 to 25 mbar; withdrawing an oligomer solution comprising ahigh molecular weight polycarbonate oligomer having a weight averagemolecular weight of 8 to 20 kilodaltons based on polystyrene standardsand a viscosity of greater than or equal to 1 Pa·s; and directing thehigh molecular weight polycarbonate oligomer to a series ofpolymerization vessels; wherein at least of the first oligomeriser andthe second oligomeriser are described by the reactor of any one or moreof Embodiments 1 to 4.

Embodiment 14: The method of Embodiment 15, wherein the firstoligomeriser and the second oligomeriser are described by the reactor ofany one or more of Embodiments 1 to 4.

Embodiment 15: The method of Embodiment 15, wherein the firstoligomeriser is a side feed oligomeriser and the second oligomeriser isdescribed by the reactor of any one or more of Embodiments 1 to 9;wherein the first oligomeriser has two three-blade impellers extendingfrom the stirring shaft and the second oligomeriser has a flat plateimpeller extending from the stirring shaft.

Embodiment 16: Use of the reactor of any one or more of Embodiments 1 to4 in polymerizing a polycarbonate oligomer.

Embodiment 17: The reactor of any one or more of further comprising acontroller configured to control at least one of a flow rate, apressure, or a temperature in the reactor.

The compositions, methods, and articles can alternatively comprise,consist of, or consist essentially of, any appropriate materials, steps,or components herein disclosed. The compositions, methods, and articlescan additionally, or alternatively, be formulated so as to be devoid, orsubstantially free, of any materials (or species), steps, or components,that are otherwise not necessary to the achievement of the function orobjectives of the compositions, methods, and articles.

The terms “a” and “an” do not denote a limitation of quantity, butrather denote the presence of at least one of the referenced items. Theterm “or” means “and/or” unless clearly indicated otherwise by context.Reference throughout the specification to “an embodiment”, “anotherembodiment”, “some embodiments”. “an aspect”, and so forth, means that aparticular element (e.g., feature, structure, step, or characteristic)described in connection with the embodiment is included in at least oneembodiment described herein, and may or may not be present in otherembodiments. In addition, it is to be understood that the describedelements may be combined in any suitable manner in the variousembodiments. “Optional” or “optionally” means that the subsequentlydescribed event or circumstance may or may not occur, and that thedescription includes instances where the event occurs and instanceswhere it does not. The term “combination” is inclusive of blends,mixtures, alloys, reaction products, and the like. The suffix “(s)” asused herein is intended to include both the singular and the plural ofthe term that it modifies, thereby including one or more of that term(e.g., the colorant(s) includes one or more colorants). Unlessspecifically stated, the terms “first,” “second,” and the like,“primary,” “secondary,” and the like, as used herein do not denote anyorder, quantity, or importance, but rather are used to distinguish oneelement from another. Also, “at least one of” means that the list isinclusive of each element individually, as well as combinations of twoor more elements of the list, and combinations of at least one elementof the list with like elements not named.

In general, the compositions, methods, and articles can alternativelycomprise, consist of, or consist essentially of, any ingredients, steps,or components herein disclosed. The compositions, methods, and articlescan additionally, or alternatively, be formulated, conducted, ormanufactured so as to be devoid, or substantially free, of anyingredients, steps, or components not necessary to the achievement ofthe function or objectives of the present claims.

The endpoints of all ranges directed to the same component or propertyare inclusive of the endpoints, are independently combinable, andinclude all intermediate points and ranges. For example, ranges of “upto 25 wt %, or 5 to 20 wt %” is inclusive of the endpoints and allintermediate values of the ranges of “5 to 25 wt %,” for example, 10 to23 wt %, etc.

Unless defined otherwise, technical and scientific terms used hereinhave the same meaning as is commonly understood by one of skill in theart to which this invention belongs. All cited patents, patentapplications, and other references are incorporated herein by referencein their entirety. However, if a term in the present applicationcontradicts or conflicts with a term in the incorporated reference, theterm from the present application takes precedence over the conflictingterm from the incorporated reference.

While particular embodiments have been described, alternatives,modifications, variations, improvements, and substantial equivalentsthat are or may be presently unforeseen may arise to applicants orothers skilled in the art. Accordingly, the appended claims as filed andas they may be amended are intended to embrace all such alternatives,modifications variations, improvements, and substantial equivalents.

1. A reactor (10) for carrying out a melt transesterification reaction at a reactor temperature of 160 to 300° C. and a reactor pressure of 5 to 200 mbar, comprising: a cylindrical tank (12) comprising a top, a side, and a bottom, wherein the bottom is convex, extending away from the top; a stirring shaft (14) disposed within the cylindrical tank (12) along an axis (100) thereof so that it is rotatable from outside of the cylindrical tank (12); a stirring blade (16) extending from the stirring shaft (14) in the cylindrical tank (12); a reactant solution inlet (40) located on the bottom; and a reaction solution outlet (20) located on the bottom, wherein the stirring blade comprises a flat plate impeller.
 2. The reactor of claim 1, wherein the reaction solution outlet (20) is concentrically located on the axis (100) of the cylindrical tank (12).
 3. The reactor of claim 1, wherein the flat plate impeller has a plurality of openings (18).
 4. The reactor of claim 1, wherein the stirring blade (16) comprises a three-blade impeller. 5-13. (canceled) 